Impact of Climate Change on Regional Hydroclimate Projection in Peninsular Malay
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Mohd Ekhwan Toriman1, Mazlin Bin Mokhtar2, Rahmah El-fithri2, Nor Azlina Abdul Aziz1, Md. Pauzi Abdullah3 and Muhamad Barzani Gasim4
1. School of Development and Environmental Studies, FSSK University Kebangsaan Malaysia, Bangi Selangor 43600, Malaysia
2. Institute for Environment and Development (LESTARI), University Kebangsaan Malaysia, Bangi Selango 43600, Malaysia
3. School of Chemical Sciences and Food Technology, University Kebangsaan Malaysia, Bangi Selangor 43600, Malaysia
4. School of Environmental Sciences and Natural Resources, University Kebangsaan Malaysia, Bangi Selangor 43600, Malaysia
Received: April 6, 2011 / Accepted: June 8, 2011 / Published: January 20, 2012.
Abstract: For the assessment of the impact of future climate change on the hydrologic regime and water resources of Peninsular Malaysia, it is necessary to downscale the climate change simulations of a coarse scale General Circulation Model to the region of Peninsular Malaysia at fine grid resolution. This paper presents a desktop review of the state of climate change parameters, namely rainfall and river flow over the Peninsular Malaysia for the 2041-2050 projection period. Analysis of the results from the models shows there will be a substantial increase in mean monthly precipitation over the North East Coastal region from historical 259.5 mm to 281.5 mm, from 289.0 mm to 299.0 mm and 221.8 mm to 239.5 mm over Terengganu and Kelantan, respectively. Meanwhile, for river flow projection, it will be an expected increase in interannual and intraseasonal variability with increased hydrologic extremes(higher high flows, and lower low flows) at Kelantan, Pahang, Terengganu, and Kedah watersheds in the future.
Key words: Climate change, peninsular Malaysia, rainfall, river flow.
1. Introduction??
In 2007, the International Panel on Climate Change(IPCC) considered data from climate observations across the world and concluded that the evidence for warming of the global climate is “unequivocal”. Current projections estimate that the increase in global temperature by the end of this century will range from 1.8-4.0 oC predominantly depending on the level of future greenhouse gas emissions. However, these figures demonstrate that dangerous climate change-conventionally understood as a global temperature rise of 2 °C or greater-is becoming increasingly likely. And even this picture is evolving rapidly: recent studies suggest that the impacts of climate change may be even more severe and more rapid than those reported by the IPCC at the start of 2007. Whilst many reports of climate change focus on rising temperature, global warming means more this: climate change affects all aspects of the climate, making rainfall less predictable, changing the character of the seasons and increasing the likelihood or severity of extreme events such as cyclones and floods [1]. Worse, the impact of these changes is often aggravated by existing environmental problems, such as when deforestation and extreme rainfall combine to produce landslides or floods.
In general, weather and climate are among the foremost factors that determine how a society develops in a geographical region [2-4]. Daily fluctuations of the atmosphere are called weather while climate is typically the average state of the atmosphere observed over a finite time period for a number of years. The social, economical and physical infrastructure of a geographical region (such as Malaysian Peninsular) has evolved from the adaptation of that region’s society to the prevailing climate and to the hydrological conditions brought about by that climate over decades or, as in the case of Peninsular Malaysia, over centuries. The frequency of occurrence and magnitudes of such phenomena as typhoons, floods and droughts have a profound influence on the habitability of a region and on the social and economical activities of that region’s population which tries to moderate the stresses brought about by those climatic/hydrological extreme events.
Meanwhile, the regional climate change refers to decades-long trends in regional climate. The future impacts of climate change on the hydrology of a geographical region needs to be studied in order to quantify in detail the potential changes which may occur in hydrological water balances in that region due to such a climate change. This paper presents a desktop review on the future simulation of the hydroclimate over Peninsular Malaysia during 2041-2050 period and compared against the CGCM1/RegHCM-PM simulated historical hydroclimate over Peninsular Malaysia during 1984-1993 in order to quantify the potential changes in hydrologic conditions over the region. In this case, two major parameters of hydroclimatology will be discussed mainly the precipitation and river flow.
Fig. 1 Data grid of CGCM1 that used in the RegHCM-PM. The ocean grids which are used in the RegHCM-PM are shown as blue. The land grids which are used in the RegHCM-PM are shown as green.
2. Study Area and Method
In this study a regional hydroclimate model of Peninsular Malaysia (RegHCM) has been developed in order to downscale the available global historical and climate change atmospheric databases (Fig. 1) that were simulated by the Canadian GCM (CGCM1) at a coarse grid resolution of about 410 km, to Peninsular Malaysia at fine spatial resolution (9 km).
Due to its well-documented validation with the historical observations over Peninsular Malaysia, and to its use of the most realistic climate change scenario(IS92a) in its climate change simulation studies, the CGCM1 climate change simulation results were selected for use in this study. The CGCM1 is a global, three-dimensional climate model, developed by CCCma by coupling the second-generation atmospheric general circulation model of CCCma [5] to a version of the GFDL (Geophysical Fluid Dynamics Laboratory) modular ocean model MOM1[6]. The atmospheric component of CGCM1 is a spectral model with T32 triangular truncation at wave number 32 (yielding a surface grid resolution of roughly 3.7° lat × 3.7° long) [7]. The size of a CGCM1 surface grid is in the order of 410 km over the Peninsular Malaysia region.
RegHCM-PM was validated by historical hydroclimate data over Peninsular Malaysia, and was used to downscale the coarse-resolution (~410 km) climate change simulations of Canadian General Circulation Model CGCM1 to this region at fine grid resolution (~9 km). RegHCM-PM was calibrated objectively from the existing land databases, and was validated by historical hydroclimatic data over Peninsular Malaysia during the 1984-1993 historical period [8].
The climate simulation data for the historical period, produced by CGCM1, were used for initial and boundary conditions for RegHCM-PM simulations of the historical hydroclimate over Peninsular Malaysia during this period, and compared against ground observations for the validation of the RegHCM-PM. The downscaled hydroclimatic data over Peninsular Malaysia for the future 2041-2050 period were then compared against the corresponding historical hydroclimatic data for the 1984-1993 period in order to assess the impact of climate change over the hydrology and water resources of Peninsular Malaysia in terms of rainfall and river flow by graphical and statistical methods. Below, the assessment of the impact of future climate change, as simulated by CGCM1 and downscaled to Peninsular Malaysia by RegHCM, on the climate and hydrology of Peninsular Malaysia is reported.
Fig. 2 Simulated annual precipitation at every subregion of Peninsular Malaysia during the simulated historical and future periods.
Table 1 Averaged historical and projection annual precipitation.
3. Results and Discussion
3.1 Long Term Rainfall Simulation
Hydrologic conditions of peninsular malaysia were simulated using RegHCM-PM in several time periods, 1984-1993 for historical conditions, and 2041-2050 for future global climate change conditions (Table 1 and Fig. 2). From Table 1, it is seen that there is a decrease in rainfall over the Southern and Central Regions, a small increase in rainfall over the northwest and northeast regions, and a small decrease in rainfall over the southern region of Peninsular Malaysia with the change region of Peninsular Malaysia with the change of climate in the future.
Some dry years (1993 and 2044) and wet years(1989, 2043, and 2049) can be discerned in annual precipitation from Fig. 2. The long-term trend of annual precipitation is not pronounced because the interannual variability in precipitation, as noted from Fig. 2, is quite large. Table 2 shows summary of simulated monthly precipitation during the historical and future periods at the selected watersheds of Peninsular Malaysia. From the table may note that there will be a substantial increase in mean monthly precipitation over the North East Coastal region over Terengganu and Kelantan. Generally, it may be inferred from this table that since higher maximum and lower minimum precipitation are observed in the future in many subregions, more extreme hydrological conditions may be expected.
3.2 Long Term River Flow Simulation
Fig. 3 shows the location of selected stream gauging used for simulating monthly river flows over the Peninsular Malaysia during the historical(1984-1993) and future (2041-2050) period. In these simulations, it is assumed that the fundamental physical characteristics of the selected watersheds(topography, land use/cover, vegetation, etc.) remain the same during the 50 years between the present and future periods, and that only the changing climate is driving the change in the hydrologic regime of the river flows.
Table 2 Summary of simulated monthly precipitation during the historical and future.
Fig. 3 River gauging stations used for simulating monthly flow.
Table 3 Summary of simulated flows during the historical and future periods at the selected watersheds of Peninsular Malaysia.
Table 3 summarizes the assessment of the simulated historical and future flow conditions in terms of maximum, mean, and minimum monthly flows at the eight selected river stations. The results indicate that the mean monthly flows stay about the same in most watersheds except in Kelantan and Pahang where it increases. From Table 3, it may be also inferred that the hydrologic extremes will be magnified significantly in Kelantan, Terengganu, and Pahang River watersheds. In the future minimum monthly flows will be lower and the maximum monthly flows will be significantly higher than their historical counterparts in these watersheds.
4. Conclusion
The challenge of climate change in Peninsular Malaysia is real and urgent. Climate change is likely to amplify some of the existing urban and environmental stresses and vulnerabilities of its urban communities, many of which are living in coastal and low-lying areas and rapidly expanding mega-cities especially in east coast region. By comparing the historical simulations of precipitation and river flow using the CGCM1/RegHCM-PM, this paper demonstrates a significant changed on both parameters during 2041-2050 projection period. The expected changes, described above, in the hydrologic regime of Peninsular Malaysia may require significant planning of the Peninsula’s water resources in order to accommodate such expected changes into the future water balances over the Peninsula. Collaboration across planning, enforcement and compliance regimes can strengthen the integration of environmental concerns into the wider development agenda.
Acknowledgments
Special thanks are given to the National Hydraulic Research Institute of Malaysia (NAHRIM) which provide all the related data. Also thank to Centre for Research and Innovation Management (CRIM), Universiti Kebangsaan Malaysia and Regional Sustainable Development niche group for general assistant.
References
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